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Storage and repair bandwidth tradeoff for heterogeneous cluster distributed storage systems

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Science China(Information Sciences) 2020年第2期63卷 131-145页

作者： Jingzhao WANG Yuan LUO kenneth W.SHUM Department of Computer Science and Engineering Shanghai Jiao Tong University Institute of Network Coding The Chinese University of Hong Kong

The storage and repair bandwidth tradeoff is an important issue in distributed storage systems(DSSs) where large scale data are stored in multiple nodes with erasure coding to ensure reliability. There are lots of studies on the DSS model with multiple clusters where the repair bandwidths from intra-cluster and cross-cluster nodes are differentiated to improve repair efficiency based on the realistic network topological structures. At the same time, separate nodes are also prevalent due to the variety of practical networks, but the work on the cluster DSS model with multiple separate nodes is insufficient, which is a main motivation of this paper. We formulate the tradeoff bound between storage repair bandwidth for a heterogeneous DSS model consisting of clusters and separate nodes by analyzing the min-cuts of heterogeneous information flow graphs corresponding to the orders of failed nodes. Additionally, the tradeoff bounds are investigated in multiple aspects when the repair bandwidth constraints and the amount of separate nodes vary, ***, a class of regenerating codes are illustrated to achieve the tradeoff in the heterogeneous cases.

关键词： distributed storage system cluster separate node repair bandwidth information flow graph

A Well-Posed and Discretely Stable Perfectly Matched Layer for Elastic Wave Equations in Second Order Formulation

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Communications in Computational Physics 2012年第5期11卷 1643-1672页

作者： kenneth Duru Gunilla Kreiss Division of Scientific Computing Department of Information TechnologyUppsala UniversityBox 337SE-75105 UppsalaSweden

We present a well-posed and discretely stable perfectly matched layer for the anisotropic(and isotropic)elastic wave equations without first re-writing the governing equations as a first order *** new model is derived by the complex coordinate stretching *** standard perturbation methods we show that complex frequency shift together with a chosen real scaling factor ensures the decay of eigen-modes for all relevant *** buttress the stability properties and the robustness of the proposed model,numerical experiments are presented for anisotropic elastic wave *** model is approximated with a stable node-centered finite difference scheme that is second order accurate both in time and space.

关键词： Perfectly matched layer well-posedness stability hyperbolicity elastic waves

Conversion of natural marine skeletons as scaffolds for bone tissue engineering

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Frontiers of Materials Science 2013年第2期7卷 103-117页

作者： Xing ZHANG kenneth S. VECCHIO Department of Bioengineering Rice University Houston Texas 77030 USA Department of NanoEngineering University of California at San Diego La Jolla California 92093 USA

Marine CaCO3 skeletons have tailored architectures created by nature, which give them structural support and other functions. For example, seashells have dense lamellar structures, while coral, cuttlebone and sea urchin spines have interconnected porous structures. In our experiments, seashells, coral and cuttlebone were hydrothermaily converted to hydroxyapatite （HAP）, and sea urchin spines were converted to Mg-substituted tricalcium phosphate, while maintaining their original structures. Partially converted shell samples have mechanical strength, which is close to that of compact human bone. After implantation of converted shell and spine samples in rat femoral defects for 6 weeks, there was newly formed bone growth up to and around the implants. Some new bone was found to migrate through the pores of converted spine samples and grow inward. These results show good bioactivity and osteoconductivity of the implants, indicating the converted shell and spine samples can be used as bone defect fillers. The interconnected porous HAP scaffolds from converted coral or cuttlebone that have pore size larger than 100μm likely support infiltration of bone cells and vessels, and finally encourage new bone ingrowth.

关键词： seashell sea urchin spine coral cuttlebone hydrothermal conversion hydroxyapatite (HAP) β-tricalcium phosphate (-TCP)

The performance of stochastic designs in wellbore drilling operations

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Petroleum Science 2018年第2期15卷 335-365页

作者： kenneth Imo-lmo Eshiet Yong Sheng School of Civil Engineering University of LeedsLeeds LS2 9JTUK

Wellbore drilling operations frequently entail the combination of a wide range of variables. This is underpinned by the numerous factors that must be considered in order to ensure safety and productivity. The heterogeneity and sometimes unpredictable behaviour of underground systems increases the sensitivity of drilling activities. Quite often the operating parameters are set to certify effective and efficient working processes. However, failings in the management of drilling and operating conditions sometimes result in catastrophes such as well collapse or fluid loss. This study investigates the hypothesis that optimising drilling parameters, for instance mud pressure, is crucial if the margin of safe operating conditions is to be properly defined. This was conducted via two main stages： first a deterministic analysis--where the operating conditions are predicted by conventional modelling procedures--and then a probabilistic analysis via stochastic simulations--where a window of optimised operation conditions can be obtained. The outcome of additional stochastic analyses can be used to improve results derived from deterministic models. The incorporation of stochastic techniques in the evaluation of wellbore instability indicates that margins of the safe mud weight window are adjustable and can be extended considerably beyond the limits of deterministic predictions. The safe mud window is influenced and hence can also be amended based on the degree of uncertainty and the permissible level of confidence. The refinement of results from deterministic analyses by additional stochastic simulations is vital if a more accurate and reliable representation of safe in situ and operating conditions is to be obtained during wellbore operations.

关键词： Well stability Stochastic analysis Deterministic analysis Mud pressure Safe mud window Wellbore drilling Rock properties

Validity of the Africa-wide Lang factor of 2.63 for estimating small biogas plant installation costs in Uganda

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International Journal of Agricultural and Biological Engineering 2014年第1期7卷 70-76页

作者： kenneth Ndyabawe William S.Kisaalita College of Engineering University of GeorgiaAthensGA 30602USA

There is an increasing interest in popularizing small biogas plants to meet the bulk of domestic energy needs in Africa for cooking,lighting,and other activities such as cooling or *** stakeholders(policy makers,donors,credit providers,sector experts,and product development professionals)contemplate programs,one of the key questions to which a reliable answer is needed is biogas plant installation cost that may vary from region to *** Africa-wide materials’cost multiplier factor(Lang factor of 2.63)estimation approach has been proposed,based on data from only two *** factor’s validity throughout Africa has been *** study shows that the Africa-wide Lang factor of 2.63 is applicable in ***,differences in accuracy have been observed based on whether the installation is located in a rural or urban ***-specific factors of 2.984 and 2.404 for rural and urban locations were established and validated,respectively,which produced more accurate estimates in comparison with a single composite non-location specific factor.

关键词： biogas fixed capital investment Lang factor Uganda renewable energy

Numerical simulation of a possible origin of the positive radial metallicity gradient of the thick disk

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Research in Astronomy and Astrophysics 2014年第11期14卷 1406-1414页

作者： Awat Rahimi kenneth Carrell Daisuke Kawata National Astronomical Observatories Chinese Academy of Sciences Mullard Space Science Laboratory University College London Holmbury St.Mary DorkingSurrey RH5 6NT UK

We analyze the radial and vertical metallicity and [α/Fe] gradients of the disk stars of a disk galaxy simulated in a fully cosmological setting with the chemo- dynamical galaxy evolution code GCD＋. We study how the radial abundance gradients vary as a function of height above the plane and find that the metallicity （[α/Fe]） gra- dient becomes more positive （negative） with increasing height, changing sign around 1.5 kpc above the plane. At the largest vertical height （2 〈丨z丨〈 3 kpc）, our simulated galaxy shows a positive radial metallicity gradient. We find that the positive metallicity gradient is caused by the age-metallicity and age-velocity dispersion relation, where younger stars have higher metallicity and lower velocity dispersion. Due to the age- velocity dispersion relation, a greater fraction of younger stars reaches 丨z丨〉 2 kpc at the outer region, because of the lower gravitational restoring force of the disk, i.e. flaring. As a result, the fraction of younger stars with higher metallicity due to the age-metallicity relation becomes higher at the outer radii, which makes the median metallicity higher at the outer radii. Combining this result with the recently observed age-metallicity and age-velocity dispersion relation for the Milky Way thick disk stars suggested by Haywood et al., we argue that the observed （small） positive radial metal- licity gradient at large heights of the Milky Way disk stars can be explained by flaring of the younger thick and/or thin disk stars.

关键词： Galaxy disk -- Galaxy kinematics and dynamics -- galaxies interac-tions- galaxies formation- galaxies evolution- galaxies abundances

Predicting the mode of flow in pneumatic conveying systems—A review

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Particuology 2008年第5期6卷 289-300页

作者： Mark G.Jones kenneth C.Williams Centre for Bulk Solids and Particulate Technologies School of EngineeringUniversity of NewcastleNewcastle 2308Australia

An initial prediction of the particulate mode of flow in pneumatic conveying systems is beneficial as this knowledge can provide clearer direction to the pneumatic conveying design process. There are three general categories of modes of flow, two dense flows： fluidised dense phase and plug flow, and dilute phase oniy. Detailed in this paper is a review of the commonly used and available techniques for predicting mode of flow. Two types of predictive charts were defined： basic particle parameter based （e.g. particle size and density） and air-particle parameter based （e.g. permeability and de-aeration）. The basic particle techniques were found to have strong and weak areas of predictive ability, on the basis of a comparison with data from materials with known mode of flow capability. It was found that there was only slight improvement in predictive ability when the particle density was replaced by loose-poured bulk density in the basic parameter techniques. The air-particle-parameter-based techniques also showed well-defined regions for mode of flow prediction though the data set used was smaller than that for the basic techniques. Also, it was found to be difficult to utilise de-aeration values from different researchers and subsequently, an air-particle-based technique was developed which does not require any de-aeration parameter in its assessment.

关键词： Pneumatic conveying Mode of flow Dense phase Permeability De-aeration

Power regulation of kinematic control inputs for forward flying Drosophila

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Acta Mechanica Sinica 2014年第6期30卷 809-818页

作者： kenneth MacFarlane Imraan Faruque J.Sean Humbert 3181 Glenn L Martin Hall University of MarylandCollege Park MD 20742 USA

The choices of insect wing kinematic programs is not well understood,particularly the mechanism by which an insect selects a distortion to achieve flight control.A methodology to evaluate prospective kinematic control inputs is presented based on the reachable states when control actuation was constrained to a unit of *** method implements a computationally-derived reduced order model of the insect’s flight dynamics combined with calculation of power *** kinematic inputs are evaluated based on this criterion for a Drosophila size insect in forward *** bias is shown to be the dominant control input using this power normalized evaluation measure.

关键词： Flight control Control Drosophila Power

The emerging roles of microRNAs in the molecular responses of metabolic rate depression

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分子细胞生物学报:英文版 2011年第3期3卷 167-175页

作者： Kyle K.Biggar kenneth B.Storey Institute of Biochemistry and Department of Biology Carleton University1125 Colonel By DriveOttawaONCanada K1S 5B6

Metabolic rate depression is an important survival strategy for many animal species and a common element of hibernation,torpor,estivation,anoxia and *** of the molecular mechanisms that regulate reversible transitions to and from hypometabolic states have identified principles of regulatory *** control mechanisms are conserved among biologically diverse organisms and include the coordinated reduction of specific groups of key regulatory enzymes or proteins in the cell,a process likely driven by microRNA target repression/*** present review focuses on a growing area of research in hypometabolism and mechanisms involving the rapid and reversible control of translation facilitated by *** analysis draws primarily from current research on three animal models:hibernating mammals,anoxic turtles and freeze-tolerant frogs(with selected examples from multiple other sources).Here,we demonstrate a link between metabolic rate depression,a well-documented response to periods of environmental stress,and microRNA ***-based expression profiles and PCR-driven studies have revealed that specific microRNAs are induced in response to environmental *** members of this group decrease pro-apoptotic signaling,reduce muscle wasting and reduce protein translation,whereas other members contribute to cell cycle arrest and mitogen-activated protein kinase *** of the same microRNAs are frequently deregulated in numerous disease pathologies and,hence,the hypometabolism model could provide a novel approach for the treatment of stroke and heart attack in humans.

关键词： microRNA metabolism metabolic rate depression protein translation muscle atrophy cell cycle apoptosis